DESCRIPTION: Of an estimated 1.5 million American children with Pb poisoning, more than 90% will have mild to moderately elevated blood Pb levels between 10 and 44 mcg/dl. Pb in this range can cause biochemical and neurodevelopmental toxicity in young children; cognitive deficits can persist for many years after the acute period of Pb ingestion. On the other hand, an active intervention to lower blood Pb levels over a 6-month period has been shown to be associated with improved cognitive scores in preschool children. Currently, treatment modalities for children with mild-moderate Pb poisoning are limited. Although environmental efforts to reduce Pb exposure are an effective means for reducing further Pb ingestion, they are often difficult to initiate and complete successfully, especially for children living in urban, poor neighborhoods. The ability of chelating agents to permanently reverse biochemical and cognitive toxicity for mild to moderately Pb-poisoned children has not been demonstrated. Ca is known to interact with Pb at multiple biological levels: Pb interferes with intracellular Ca-mediated processes; Ca and Pb compete for binding to what are normally Ca-binding proteins. Nutritionally, diets deficient in Ca enhance the absorption of Pb; blood Pb levels in children are inversely related with Ca intake. This information serves as a basis to begin an investigation of the effect of Ca supplementation as a treatment component for childhood Pb poisoning. In a pilot study, moderately Pb-poisoned children, supplemented with Ca to reach a daily intake of 1800 mg, had a fall in their blood Pb levels over 3 months that was more than twice that of unsupplemented controls. This study is proposed to define the role of Ca supplementation as a treatment for children with mild to moderate Pb poisoning. It will use a prospective, randomized, placebo-controlled study design. Supplementation will be aimed to achieve a daily intake of 1800 mg of Ca (diet plus supplement) in the experimental group. Treatment will continue for 3 months, to be followed by an additional 3 month observation period. Change in blood Pb will be the main outcome measure. Ca treatment is posited to decrease Pb absorption, thereby contributing to a fall in blood Pb levels. Thus, Ca supplementation might provide a cost-effective and readily-available treatment that will be of benefit to the millions of children worldwide who continue to be exposed to excessive amounts of Pb and who remain at risk for its toxic effects.